Currently, there are 16 mm rotary microfilmers that capture document images on film of both sides (duplex operation) at reductions of 42.times. or 50.times. or even greater reductions. Both sides of the document are filmed side by side on the same roll of film. However, at a reduction of 25.times. or less, both sides of the document image cannot fit side by side onto 16 mm film. Currently, at this reduction, microfilmers capture one side of a document only (simplex operation). The document must be turned over after the first filming and refed in order to record both sides of the document. Because of the large volumes of documents involved, this becomes very labor intensive and susceptible to operator error.
Because many organizations microfilm documents containing very small characters or symbols and to insure readability upon retrieval, a higher resolution 25.times. lens is used.
Canadian Pat. No. 545,970 entitled "Apparatus for Photographically Copying Both Sides of a Document" discloses the photographing of both sides of a document simultaneously, side by side onto two rolls or one wide roll of microfilm. The use of two rolls provides a duplicate copy. The document is advanced through a photographing station where both sides are illuminated by a separate set of lamps. Both sides of the document are then imaged onto a photosensitive medium by three lenses and a mirror system. The disadvantage of such a system is that it is limited by the optical reduction ratio. The reduction ratio must be equal to or greater than a reduction ratio that will allow front and rear images when placed next to one another to be narrower than the width of the film usually 16 mm. Accordingly, one is limited to a reduction ratio of 42.times. for 16 mm film format. By using three lenses, this system is limited by the document width that will fit next to each other when imaged on a single roll of film.
U.S. Pat. No. 3,885,871 entitled "Document Photography System" illustrates a system where both sides of a document are photographed simultaneously with images thereof placed in side by side relationship onto a roll of film in which the width of the document is sensed and the film motion is incremented by amounts proportional to the indicated width of the documents. With such a system, documents of unlimited width may be photographed. Once again, the disadvantage is the same as described in the previous patent. The optical reduction ratio is once again the limiting factor. The reduction ratio must be such that the combined size of the images of both sides of the document in the "across the film" or "cross track" direction are smaller than the width of the photosensitive media.